EFFECTS OF PLASTIC MULCHES ON GROWTH AND YIELD OF CUCUMBER (CUCUMIS-SATIVUS L.) AND ON NEMATODE AND MICROBIAL-POPULATION DENSITIES IN THE SOIL

The growth and yield of three crops of cucumber and rhizosphere popula tions of soil nematodes were monitored in an experiment conducted on s andy loam soil which was (a) mulched with 0.4-mm-thick, clear or black plastic for five or nine weeks, (b) mulched then fertilized with 1 kg N:P:K (4:16:4)/plot, (c) not mulched and treated with 45 g Banrot 40W P/plot or 10 or 20 g Furadan 10G/plot at planting, (d) not mulched, bu t fertilized, (e) not mulched and not fertilized. In a second experime nt, plots were mulched for four, six and eight weeks with clear or bla ck plastic or not mulched. Ambient and soil temperatures were monitore d during the mulching periods. Cucumber seedlings in the fertilized or nonfertilized plots which were mulched with either color of plastic o ften grew faster than those in the nonmulched plots. Plants from plots treated with fungicide or nematicide either had shoots which were sho rter or of the same lengths as those from the nontreated plots. Plants from nonfertilized plots mulched for four or more weeks with clear pl astic yielded more than the controls in Experiment 2; whereas, with bl ack plastic, only plots mulched for six or eight weeks yielded more th an the controls. Population densities of fungi in soil mulched with cl ear plastic were lower than those in nontreated soil, but those of bac teria were similar. Phytoparasitic and nonparasitic nematode populatio n densities were reduced by the nematicide and by mulching with either color of plastic, but sometimes rose to the initial levels by the tim e of harvest. Plastic mulching significantly controlled weed growth bu t many of the monocotyledonous plants in the field grew in soil under the clear plastic.